I also assumed it was an exchange or another sort of company changing wallets to ensure the security or something like that, but since you're claiming it's Bittrex, proof would be nice. Anyway, I've googled it and I think I've found it, so I'm attaching it here:
https://cointelegraph.com/news/almost-9-billion-of-bitcoin-moved-on-chain-in-1-hour-record.
I don't think that whale alert makes sense, most of the time it turns out to be a technical operation... I don't even believe that there are 'whales' that can manipulate the market significantly, it's just a chain reaction with separate entities most of the time we see the price changing.
I'd be scared if it was a personal holding

$10 billion it must be corporate funds. satoshi himself own 1 million bitcoin worth 7.523.610.000 around 7.5 billion , who else holding more than 1 million bitcoin? i don't think anybody does have it in their personal wallet.
this is just an ordinary funds transfer , end of story.
some people taking advantage on this by linking to how the fund prepared for market dump, that is just random.